Method for producing hot strips from lightweight steel

Abstract

In a method for producing hot strips from a deformable lightweight steel which includes as main elements Fe, Mn, Si and Al, melt is cast close to its final dimension in a horizontal continuous strip casting installation under a protective gas to form a pre-strip between 6 and 20 mm, and the temperature of the pre-strip is adjusted after complete solidification and before the beginning of a hot-rolling process. The pre-strip is passed through a device under a protective gas for homogenization in concert with a selective maintenance of the temperature, cooling or heating, and subsequently subjected to a hot-rolling process having at least one pass with a total degree of deformation of at least 50%, and is then reeled as a hot strip following the cooling process. The hot-rolling process is executed in-line or in decoupled manner depending on the ratio of casting speed to rolling speed.

Description

BACKGROUND OF THE INVENTION[0001]The invention relates to a method for producing hot strips from a deformable lightweight steel which is especially suitable for cold deep drawing and includes as main elements Fe, Mn, Si and Al and which has a high tensile strength and TRIP and / or TWIP properties.[0002]The method, set forth in the preamble, for producing hot strips from a deformable lightweight steel which is especially suitable for cold deep drawing is known (steel research 74 (2003), No. 11 / 12, pp 724-731).[0003]The production of such steels of high manganese content has been marred by problems to ensure a fine-grained and isometric microstructure.[0004]DE 197 58 108 C1 discloses a production method and production installation for continuous production of hot-rolled thin flat products. Melt from steel that has not been designated in greater detail is cast in a horizontal continuous strip installation close to its final dimension in a range between 5-18 mm and cooled in a controlled...

AI Technical Summary

Benefits of technology

[0008]It is an object of the invention to provide a method for producing hot strips from a deformable lightweight steel which is especially suitable for cold deep drawing and which allows a reliable realization of a fine-grained, preferably isometric microstructure.

[0016]The proposed decoupling has the advantage that the casting speed can be selected in dependence on the alloy composition of the steel with respect to optimum solidification conditions, regardless of the cycle of the subsequent hot rolling process. In contrast thereto, the afore-mentioned in-line hot rolling has, however, the advantage of increased productivity, whereby the final thickness may be realized by the rolling operation either throughout or partway.

[0018]When a decoupled operation is involved, the pre-strip is directly reeled in the simplest case after complete solidification and passage through the homogenization zone. This assumes that the casting structure of the pre-strip is so configured as to enable reeling and unreeling. Normally, the pre-strip is subjected to a first pass which is sufficient to effect at least a partial crystallization of the outer regions of the strip in order to be able to easily reel the strip.

[0022]All thus-produced hot strips can be deep-drawn cold, and targeted cold forming processes (e.g. rolling, stretching, deep drawing) with optional interposed annealing processes make it possible to adjust a wide spectrum of different properties with respect to strength, ductility, and structural isometry.

Problems solved by technology

The production of such steels of high manganese content has been marred by problems to ensure a fine-grained and isometric microstructure.

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